Long-Term Landscape Change and Bird Abundance in Amazonian Rainforest Fragments

Abstract:  The rainforests of the Amazon basin are being cut by humans at a rate >20,000 km²/year, leading to smaller and more isolated patches of forest, with remaining fragments often in the range of 1–100 ha. We analyzed samples of understory birds collected over 20 years from a standardized mist-netting program in 1– to 100-ha rainforest fragments in a dynamic Amazonian landscape near Manaus, Brazil. Across bird guilds, the condition of second growth immediately surrounding fragments was often as important as fragment size or local forest cover in explaining variation in abundance. Some fragments surrounded by 100 m of open pasture showed reductions in insectivorous bird abundance of over 95%, even in landscapes dominated by continuous forest and old second growth. These extreme reductions may be typical throughout Amazonia in small (≤10 ha), isolated fragments of rainforest. Abundance for some guilds returned to preisolation levels in 10- and 100-ha fragments connected to continuous forest by 20-year-old second growth. Our results show that the consequences of Amazonian forest loss cannot be accurately described without explicit consideration of vegetation dynamics in matrix habitat. Any dichotomous classification of the landscape into "forest" and "nonforest" misses essential information about the matrix.     

基于RS和GIS的武汉市生态系统服务价值变化研究

以武汉市为例,利用从1996年和2001年TM数据中获取的景观数据,估算了武汉市生态服务价值并分析了景观之间的转化所引起的生态服务价值的变化。结果表明:各景观类型中水域景观的生态服务价值贡献系数最大,达到2.869;研究区域生态服务价值总量变化不大,2001年比1996年只下降了3688.79万元,但各景观生态服务价值变动很大,其中库塘生态服务价值增加了2.38亿元,河流的生态服务价值减少了2.33亿元,其变化率分别达到40.74%和-9.16%;由于河湖被占用所造成的生态服务价值损失达到9891.68万元,城市建设占用其它景观类型所带来的生态服务价值损失达到9908.37万元,这说明建设用地的发展对其他自然景观占用已经影响到了武汉市生态系统服务功能发挥。     

辽河三角洲湿地景观空间格局变化分析

以1988年和2001年2个时相的Landsat-TM/ETM影像为信息源,选取斑块数量、斑块平均面积、边界密度、斑块密度、形态指数和斑块分维数等6个代表性格局指数,对辽河三角洲湿地景观格局变化进行了定量分析。结果表明,1988~2001年,水田、内陆水体和养殖用地呈现明显的增加趋势,苇田、光滩、河口潮间带水域和碱蓬面积呈减少趋势。受人类的区域综合开发活动的影响,研究区斑块数量和边界密度分别增加了32.76%和21.4%,而斑块平均面积减小了30.2%,平均斑块密度由17.43个/km2增加至24.21个/km2,斑块形态指数由84.03增至103.20,斑块分维数由1.057增至1.059。     

武夷山风景名胜区景观要素斑块特征分析

针对近年来开展生态旅游等人类活动的强烈干扰给风景区带来巨大生态影响的问题，在武夷山风景名胜区景观类型划分的基础上，从景观要素斑块特征的角度对武夷山风景名胜区的景观格局及破碎化进行初步的研究，以期为今后武夷山风景名胜区的景观生态保护提供科学的依据．研究结果表明，在武夷山风景名胜区中，马尾松林、茶园与农田是风景区中3个主要景观类型，三者面积与周长之和分别占全区的84．581％和81．669％；景观要素的面积、周长、斑块数的分布极不平衡，尤其在3类主要景观类型中，在斑块面积、周长方面差异显著；各景观要素面积与周长的分布极为相似，而斑块数的分布却没有明显的规律性；景观要素面积、周长、斑块数等斑块特征分析表明，茶园、居住地、经济林等人工或半人工经营景观的破碎化程度高，而马尾松各天然林景观的破碎化程度低，从而证明了人类经营活动的干扰是导致自然风景区景观破碎的主要因素之一．表3参18     

Demographic Limitations of the Ability of Habitat Restoration to Rescue Declining Populations

Abstract:  Habitat restoration is often recommended in conservation without first evaluating whether populations are in fact habitat limited and thus whether declining populations can be stabilized or recovered through habitat restoration. We used a spatially structured demographic model coupled with a dynamic neutral landscape model to evaluate whether habitat restoration could rescue populations of several generic migratory songbirds that differed in their sensitivity to habitat fragmentation (i.e., severity of edge effects on nesting success). Simulating a best-case scenario, landscapes were instantly restored to 100% habitat before, at, or after habitat loss exceeded the species' vulnerability threshold. The vulnerability threshold is a measure of extinction risk, in which the change in population growth rate ( δλ ) scaled to the rate of habitat loss ( δh ) falls below −1% ( δλ/δh ≤ −0.01). Habitat restoration was most effective for species with low-to-moderate edge sensitivities and in landscapes that had not previously experienced extensive fragmentation. To stabilize populations of species that were highly edge sensitive or any species in heavily fragmented landscapes, restoration needed to be initiated long before the vulnerability threshold was reached. In practice, habitat restoration is generally not initiated until a population is at risk of extinction, but our model results demonstrate that some populations cannot be recovered at this point through habitat restoration alone. At this stage, habitat loss and fragmentation have seriously eroded the species' demographic potential such that halting population declines is limited more by demographic factors than the amount of available habitat. Evidence that populations decline in response to habitat loss is thus not sufficient to conclude that habitat restoration will be sufficient to rescue declining populations.     

Virtual Corridors for Conservation Management

Abstract:  Corridors are usually perceived as clearly visible, linear landscape elements embedded in a hostile environment that connect two or more larger blocks of habitat. Animal response to certain aspects of landscape heterogeneity, however, can channel their movements into specific routes that may appear similar to their surroundings. These routes can be described as "virtual corridors" (VCs). Here we contribute to the foundation of the concept of VCs and highlight their implications for conservation management. We used an individual-based model to analyze the formation of VCs in the case of hilltopping in butterflies—where males and virgin females ascend to hilltops and mate. We simulated butterfly movements in two different topographically heterogeneous landscapes. We analyzed the movement patterns with respect to one parameter, the intensity of response to topography. Virtual corridor structure depended on the behavioral parameter, landscape, and location of the source patch. Within a realistic range of the behavioral parameter and in a realistic landscape, VC structures may be complex and require individual-based models for their elucidation.     

深圳市盐田区植被格局分析

运用景观生态学的方法 ,选取斑块形状指数、斑块形状破碎化指数、分维数、景观多样性指数、均匀度、相对丰富度、优势度等指标 ,对深圳盐田区的植被格局进行分析。结果显示 :在城乡发展过程中 ,盐田区植被景观保存较好 ,类型丰富 ;植被景观总体上呈现出符合其生境特征的规则分布 ;群落景观异质性较高 ,拥有南亚热带的沟谷雨林、山地常绿阔叶林、红树林等特色植被景观 ;沟谷雨林和季风常绿林是本区较脆弱的生态系统 ,应积极加以保护和发展     

Modeling the Hydroclimatic Disturbance of Soil Landscapes in the Southern Canadian Plains: The Problems of Scale and Place

The sensitivity of soil landscapes to climatic variability andhydroclimatic events can be expressed as a landscape change safety factor, the ratio of potential disturbance to resistance to change. The use of a geographic information system (GIS) enables the spatially-explicit modeling of landscape sensitivity, but also raises the risk of violating the characteristic scales of disturbance and resistance, because the GIS technically simplifies the extrapolation of models, and associated concepts, to landscapes and scales notrepresented by the digital data base. Embedding landscape sensitivity into hierarchy theory, the formal analysis of the hierarchical structure of complex systems, provides a conceptual framework for the transfer of models and variablesamong landscape scales. In the subhumid southern Canadian plains, major hydroclimatic events (strong winds, intense rain,rapid snow melt) cause much of the physical disturbance of soillandscapes and terrestrial ecosystems. Prolonged dry or wet weather influences the resistance of soil and vegetation to these events. The potential disturbance of soil landscapes therefore can be derived from the probabilities of extreme events and seasonal conditions, as recorded in instrumental and proxy climate records. This time series analysis can belinked to the modeling of landscape sensitivity by establishingthe probabilities of hydroclimatic events and climatic conditions which may exceed or lower the resistance of individual soil landscapes.     

Modeling Desertification Change in Minqin County,China

Monitoring environmental processes is becoming increasingly important wherever there is increasing population and economic development pressure placed on fragile environments. Remote sensing, digital image processing, and spatial analysis have proven to be useful technologies in both assessing and monitoring environmental change. In this study, they were used to assess desertification processes and change in Minqin County, China from 1988 to 1997. The results suggest that wind erosion was the dominant cause of desertification in more than half of the study area. Coupled with this were increases in salinization processes, affecting 33.62% of the land area in 1997. Overall, moderate desertification was found to be the dominant desertification grade (43.64% of total area), followed by extreme/severe desertification (26.15% of total area) in 1997. In addition, examination of landscape pattern changes indicated that desertification processes at the landscape level were becoming evident at increasing levels of fragmentation, complexity in shape, and isolation of patches. Major fluctuations in desertification type and grade were found at the fringes of oases, where an ongoing shift was taking place between cultivation, abandonment, and reclamation.     

长江三角洲国际重要湿地人为胁迫遥感解析

以长江三角洲上海崇明东滩鸟类国家级自然保护区、江苏大丰麋鹿国家级自然保护区、西溪国家湿地公园和江苏盐城国家级珍禽自然保护区4处国际重要湿地为研究对象,以Landsat MSS/TM/OLI遥感影像为基础信息源,采用面向对象的遥感分类方法获取了1980~2015年4个国际重要湿地（Ramsar）的5期土地覆被数据.通过分析湿地面积、景观格局动态及景观指数变化等,定量解析人类活动对湿地景观变化的影响,研究发现：（1）35a间,研究区内湿地面积持续减少,其中上海崇明东滩鸟类国家级自然保护区的湿地损失比例最高,为27.2%;（2）4个国际重要湿地的斑块数量和斑块密度都在增加,湿地趋于破碎化,景观间连通度降低.（3）耕地和人工表面增加是造成湿地损失的主要因素,耕地、人工表面、外来物种入侵和养殖池扩张等人为胁迫呈现上升趋势.（4）总体而言,入选国际重要湿地对人为活动有一定抑制作用,尤其是江苏大丰麋鹿国家级自然保护区湿地保护成效最为显著;但湿地保护有效性仍有待提升.